Is the ignition warning light working properly: goes on when ignition turned on, then goes out when the engine is running? If so then the battery is probably dead and needs replacing. Any good battery supplier should be able to charge up the old one and then test it to confirm this.
Fitting a voltmeter would let you keep an eye on the battery and charging circuit to give you early warning of future problems.
ShingayLodge, February 2010
